The invention relates to pumps and particularly to so-call grinder pumps typically used for pumping sewage and which includes structure for cutting of solids in the material being pumped.
Grinder pumps will be understood to be intended to grind solids such as those found in sewage so that the ground particles may be transferred through the system in smaller diameter pipes without clogging problems. One application for such pumps is in residential sewage systems where such pumps may be used between a house and a sewer transfer station or sewer main. When used in this manner, a smaller diameter pipe may be used between the house and the transfer station or sewer main without clogging problems. Thus, the cost for installing the system will be less because of the reduced size of the pipe required.
It will be understood that the present invention has particular application for use in residential applications, although various embodiments, and particularly large embodiments of the present invention, have application to use in sewage which feed into large sewer conduits as well as application for use in sewage plants themselves.
The prior art includes a variety of grinder pumps including that disclosed in U.S. Pat. No. 3,650,481. A number of other related apparatus are described in that patent.
A problem with the prior art grinder pumps is that the cutters become dull and also wear and thus increase the gap between the stationary and moving cutter elements. When the gap becomes too large, the effectiveness of the pump decreases until the pump will not function adequately.
The problems of wear and dulling of the cutters are interrelated. More specifically, as the gap becomes greater, the cutters are more subject to additional wear which not only increases the gap, but also still further decreased the sharpness of the cutters.
Those skilled in the art will understand that a clearance of 0.0025 inch or smaller is ordinarily desirable between the stationary and moving axially extending cutters. Gaps that are larger than this may allow materials such as rags to get caught in the gap thus causing the pump to stall or otherwise malfunction.
Typically, grinder pumps utilize stationary, radially extending and axially extending cutters. A stationary and radially extending cutter cut the waste into longitudinal strips. The axially extending cutters take the long strips and cut them into smaller pieces which are literally axial sections of the strips.
It is an object of the present invention to provide a grinder pump which will have a relatively long service life and particularly a grinder pump that substantially eliminates the prior art problem of wear and dullness and large gaps between the stationary and the moving cutter elements as well as repetitive adjustment of cutters, thus, eliminating repetitive manual adjustment of the cutters.
It is another object of the invention to provide apparatus which will provide a structure which will make the axial cutters and the stationary cutters associated therewith self sharpening and which will maintain the proper clearance therebetween.
It is an object of the invention to provide a grinder pump which has a longer life and requires less maintenance.